Akira can row downstream a distance of 60 kilometers in three hours. Going upstream, it takes him 4 hours to row 32 kilometers. How fast is the current?
2007-07-05 10:10:39 · 3 answers · asked by *05* 1 in Science & Mathematics ➔ Mathematics
Akira's speed = a km/hr
Speed of river current = b km/hr
Akira's relative speed:
downstream = 60/3 = 20
upstream = 32/4 = 8
Going downstream, a + b = 20
Going upstream, a - b = 8
Solving, a =14, b = 6
2007-07-05 10:16:29 · answer #1 · answered by psbhowmick 6 · 1⤊ 0⤋
Let
r = rowing speed in still water
c = speed of current
Time to row upstream 60 km = 4(60/32) = 60/8 = 7.5
distance = rate * time
60 = 3(r + c)
60 = 7.5(r - c)
20 = r + c
8 = r - c
Subtract the second equation from the first.
12 = 2c
c = 6
The current is 6 km / hour.
2007-07-05 17:18:29 · answer #2 · answered by Northstar 7 · 1⤊ 0⤋
Downstream he is going at 20km/hour
Upstream he is going 8km/hour
Presuming he is rowing at the same speed, the stream is going at 6km/hour
(the difference/2)
2007-07-05 17:17:27 · answer #3 · answered by Al 4 · 0⤊ 0⤋